You won't be getting a stable 4GHz with that C0, if using auto-settings in Vcore,Cpu PLL,Fsb Term.V. and other settings at that page in bios. My e8500 C0 has bigger multiplier as cpu ratio with 9.5x and it wasn't stable after 3.8 with anything auto.

Manual settings are the way if you really want to get that e8400 stable @ 4GHz.. Or even near stable. It's all about testing and tweaking.. it ain't that easy sometimes.. I know, because i've been fighting with this crappy e8500 for 3 weeks now

Maybe PSU could be a problem.. but i really don't believe that in your case.
My C0 is using 77w atm when i'm writing this and running IBT at the same time..
Should be pretty bad psu if not able to give that much power to cpu?
My PSU is a 500w earthwatt what came with my previous 120$ antec case

In my current setting at 3.825GHz, most of my settings in BIOS are on Auto. I do not see a reason why to change anything else, since this setting is stable. I have ran P95 and IBT and it passed. The temps are around 75C during the test, but they wont get that hot during normal usage. I can install my H-50, but Id rather return it and get my $60. My Zalman can properly cool during normal usage.

As for my attempt at 4GHz, I have tried the settings KingT has suggested. All my voltages are user inputted. Load Line Calibration was enabled. I was able to pass the large FFT test at 450x6 with Vcore at 1.35V. At 450x9, I reached my 1.4V VCore limit and the computer still froze. Any suggestions?

Well, as i wrote earlier.. it took 1.40625 from bios for me to get IBT stable with max ram and 4.037Ghz. Cpu-z was showing 1.400 in load with Load Line Calibration enabled..

Now i'm at 1.44v and 4.1+ running 15 out of 20 runs atm. Temps have peaked at 75c few times.

C0's need alot of juice usually. My chip seems to be pretty hungry for voltage
And as i said before, maybe you'd have to put some more voltage to other settings too, if it froze instead of just failing.

Interesting. Ill try that out later. I love how the BIOS can save two settings. I forgot what its called. OC Profile something.

@donrapello

At 1.4V in my 450x9 setting with IBT running, my cores shot up to 80C. This was before my computer froze. It wasnt the problem of overheating. It still froze again without anything heavy running. If I want to try to go beyond 1.4V, I may have to install my H-50. Its sitting in the box whispering, "Install me."

Yea i know that he has passed p95.. i just don't understand why it took 1.35v to pass it with such low multi.. ??? Seems pretty weird to me. Mobo problem?

As i've read, sometimes using one and the same cpu in 2-3 different mobos has needed pretty different voltage when overclocking and getting it stable. All of those were P5Q boards tested by one guy.. if i remember right, it was on the thread at this forum somewhere.. but those voltages for 6x are weird.

475 x 6 only took 1.21v for me earlier today..

And yes, he has to go beyond 1.4 to get it stable.. but how far

btw. these settings are really working with my system atm.. just passed 20 runs on IBT max ram. 4.114GHz with 484 x 8.5 .
Thanks alot for advices on stabilizing my system!

@ virus86

Right, so you really need to put that Vcore up a notch.

Just install the damn H-50.. 60$ ain't that much money
And if you think it's loud, just go and buy a couple of new fans for it
It'll probably help you with those temps.

Update: Oh my! I just installed it. I have it in a push/pull config. I have a Cooler Master R4 doing the pushing and the stock Corsair pulling. Im going to order another R4 to replace the Corsair. Plus I need to get more screws and washers. Each fan only has two screws holding it in. Here are my temps at 3.825GHz with a room temp of 21C.

Idle:
Cores = 45C
CPU = 28C

IBT Max:
Cores = 65C
CPU = 55C

Its a 10C drop across the board! With dual R4s, I might get better results. Time to test VCore>1.4V.